CL9 Poor fuel economy

My Euro has 153000ks on it and has started to get really bad fuel economy.
I have always worked out my fuel economy since purchasing the car new, and recently it has gone from 8l per 100k up to 12l per 100k. This is with exactly the same driving conditions.
I noticed my exhaust pipes seem rather black sooty colour. I have recently changed my spark plugs (they were done at 100,000k's) and the old plugs were sooty/black around the diameter and white/clean in the middle.
Is there anything in the engine that would go faulty to cause this. Is it worthwhile taking to the dealer. ???
I have checked all the obvious like leaking fuel tank, and tyre pressures.

Sound like it's running rich. Get it to a Honda service to check for fault codes.

Timing?

auto or manual?

std ecu?

id suggest the timing is out. Does it ping under load?

Auto, Standard ECU, and havent noticed any pinging.

Bad fuel?

- HZ

Doubt you'll see fault codes on this, but the primary O2 sensor can read a false lean condition, causing the injectors to put in more fuel to protect the engine. So change that or test that with a known working unit first.

no point asking if auto or manual
no point asking if it has std ecu

he has had the car since new, going for 8L to 12L per 100km.

try cleaning ur injectors, change ur fuel pump. otherwise yeah, my car was going 12L per 100km aswell, now its gone back down to 10.5

Quote:

---

Originally Posted by duzy

no point asking if auto or manual
no point asking if it has std ecu

he has had the car since new, going for 8L to 12L per 100km.

try cleaning ur injectors, change ur fuel pump. otherwise yeah, my car was going 12L per 100km aswell, now its gone back down to 10.5

---

asking because auto and manual gearboxes produce different internal loads.
increased load = decreased fuel economy.

agree could be injectors, but there a stab in the dark on a newish car and doubt they would be failing already. Your car isnt misfiring is it?

prefferable to try basic tune methods before getting drastic and changing everything straight away.

whats the weather like in your city at the moment?

8L per 100km? wow im barely pulling 9.5L/100km and i just drive on the freeway to the city and back mostly :/

i get avg of 10-11L per 100km syd city roads

ive had average down to 6.5L/100 as i drive mostly fwy to and from work
city is around 8.5L/100 (9-10L/100 with a/c on)

Also, try changing the air filter and fuel filter.. At 1530000ms.. the car should be on it's third fuel filter now.

Thanks for all your replies.
I have changed the air filter but I am reasonably sure the fuel filter has only been done once in the 153,000k's. I looked in the book on how to change fuel filter but it doesn't even say where it is, so I gave up on that.
No misfiring or anything like that.
Also anybody know how much a new O2 sensor is ???

The fuel filter is in the boot under the carpet just behind the rear seats.

5.2/100km. holla. haha.

Quote:

---

Originally Posted by aaronng

Doubt you'll see fault codes on this, but the primary O2 sensor can read a false lean condition, causing the injectors to put in more fuel to protect the engine. So change that or test that with a known working unit first.

---

I rekon aaronng is onto it here.

The best way i would say is to get your car on a dyno, light, half & full load ect to determine if the car is running rich.

They will place a sensor at the exhaust to confirm. Then, it's a matter of trial and error

Quote:

---

Originally Posted by falco

Thanks for all your replies.
I have changed the air filter but I am reasonably sure the fuel filter has only been done once in the 153,000k's. I looked in the book on how to change fuel filter but it doesn't even say where it is, so I gave up on that.
No misfiring or anything like that.
Also anybody know how much a new O2 sensor is ???

---

Silly question, but what fuel do you normally used? The Euro is specced for premium (95 octane and above). I know of people who put in the normal 91 octane and actually suffer from poor fuel economy, compounded with the fact that more and more stations now stock only the ethanol blended (E10) unleaded.

Quote:

---

Originally Posted by chrome

Silly question, but what fuel do you normally used? The Euro is specced for premium (95 octane and above). I know of people who put in the normal 91 octane and actually suffer from poor fuel economy, compounded with the fact that more and more stations now stock only the ethanol blended (E10) unleaded.

---

this is true, the E10 provides similar performance to the premium octane fuels but has the fuel economy of regular unleaded.

10.8L per 100Ks for me - normal driving condition i.e. mixture of FWY and suburbia roads. Auto with 18 inch wheels. I guess more traction on the road = less fuel economy!

i wouldnt think 18's would make that much of a difference on your euro??

ive been doing mostly suburb driving and i have been getting 6.1/100kms. im running 18x8's and 18x9's. but i spose honda claim 4.something/100kms for my car stock so...

i'm saying 02 sensor playing up.. it could be clogged and getting a bad reading, which in turn is over-fueling the engine..

Pretty much 100% back aaronng on this one,

I had the same issue with my Subaru a while back..

Quote:

---

Originally Posted by threesix

i wouldnt think 18's would make that much of a difference on your euro??

ive been doing mostly suburb driving and i have been getting 6.1/100kms. im running 18x8's and 18x9's. but i spose honda claim 4.something/100kms for my car stock so...

---

6.1 L / 100km is outstanding for suburban driving! If you get that sort of mileage driving around the city, you will get close to 1000km per full tank. Even a diesel Golf will struggle to beat that.

4.something / 100kms will be well within Prius economy territory. I don't think the Euro was ever specced for that level of economy, more like 9-10L / 100kms IIRC.

hybrid cars FTW! lol

im mega happy with my civic.

and to think i almost bought an XR6T....

Quote:

---

Originally Posted by xxb4xx

i'm saying 02 sensor playing up.. it could be clogged and getting a bad reading, which in turn is over-fueling the engine..

Pretty much 100% back aaronng on this one,

I had the same issue with my Subaru a while back..

---

I agree.This would be the 1st.thing id check.

Quote:

---

Originally Posted by chrome

6.1 L / 100km is outstanding for suburban driving! If you get that sort of mileage driving around the city, you will get close to 1000km per full tank. Even a diesel Golf will struggle to beat that.

4.something / 100kms will be well within Prius economy territory. I don't think the Euro was ever specced for that level of economy, more like 9-10L / 100kms IIRC.

---

threesix has a Civic hybrid so that's why he's getting those figures.

o2 sensor is a possibility, However I would also:

- Check Quality of Fuel
- Clean Injectors

then...

Personally to save yourself the possibility of spending useless amounts of money at the dealer/mechanic.

I would then do the following... Run a tank or at least half a tank (if you don't drive much) of E10 Petrol (Ensure you still maintain appropriate octane rating of 95 or higher) after that fill the tank with the petrol of your choice. I would recommend BP Ultimate or Mobil Synergy 8000.

Reset your ECU.

Now there are two methods of doing this both have similar testimonials to successful resets. You may choose either one! =P.

Accelerator Technique
- Turn Ignition Key to ON Position (Don't start the car)
- Turn off Accessories (Radio, Fans etc.)
- Press down the Accelerator for 30 seconds
- While holding accelerator down turn key to off (Do not remove key)
- Release the accelerator
- Wait 5 minutes then drive as you usually would.

Battery Disconnection
- Disconnect the negative (Ground) terminal of the battery. (Colour Coded BLACK)
- Press down Brake pedal a couple of times / turn on headlights to "release energy"
- Leave disconnected for over 10 minutes
- Reconnect Battery terminal
- Start car and let it idle until it reaches operating temperature
- Shut engine off
- Drive as you usually would.

Another option is to take it to a reputable mechanic who has an OBDII ECU Diagnostic Tool (90% of mechanics if not more will have one) and ask them to reset it for you! :P

Never underestimate the power of some ethanol and an ECU Reset!

If this doesn't work I would be looking at surely but slowly troubleshooting sensors, starting with the o2 Sensor.

EDIT:

If I was getting up to or over 11L/100kms in a Euro, unless you have a lot of city driving or excessive idling, i would be PISSED! The Euro doesn't have anywhere near enough power/torque to warrant 11L/100kms +

Again thanks for all the replies. I feel really stupid :o because this problem I was having was caused by poor quality fuel. I have allways filled with Caltex 95 (Premium Unleaded) but they must have recently changed the formula, as I have gone back to using BP Ultimate and I am back to 7.8l per 100K for the last two tanks.
Must be the ethanol problem we are having here in Qld

Quote:

---

Originally Posted by falco

Again thanks for all the replies. I feel really stupid :o because this problem I was having was caused by poor quality fuel. I have allways filled with Caltex 95 (Premium Unleaded) but they must have recently changed the formula, as I have gone back to using BP Ultimate and I am back to 7.8l per 100K for the last two tanks.
Must be the ethanol problem we are having here in Qld

---

Good to hear it's all sorted out.

Quote:

---

Originally Posted by falco

Again thanks for all the replies. I feel really stupid :o because this problem I was having was caused by poor quality fuel. I have allways filled with Caltex 95 (Premium Unleaded) but they must have recently changed the formula, as I have gone back to using BP Ultimate and I am back to 7.8l per 100K for the last two tanks.
Must be the ethanol problem we are having here in Qld

---

Sometimes the simplest explanation is the best. ;)

Caltex fuel is normally pretty good, especially the Vortex 98 stuff. You may have been unlucky and had a tank of fuel that was contaminated, eg with water.

- HZ

Quote:

---

Originally Posted by tony1234

threesix has a Civic hybrid so that's why he's getting those figures.

---

On a recent trip to Sydney (3075km return) i averaged 6.45L/100km with a best of 6.03. 1,000km on a tank is easily achievable & a CU2 is a much bigger, heavier car than a Civic Hybrid.

^^ your running stock rims???